The present invention is related to composite materials and methods for their manufacture using recycled, post-consumer waste polyethylene terephthalate and fly ash.
Recognizing the environmental benefits, the production and use of waste materials such as fly ash and plastics has been strongly favored by environmental agencies. High-lime fly ash (ASTM Class C fly ash) is a by-product of coal combustion in electric-generating stations that burn low sulfur sub-bituminous and lignite coals. Relatively low lime (ASTM Class F fly ash) is a by-product of coal combustion in electric-generating stations that burn high sulfur anthracite and/or bituminous coals. Millions of tons of fly ash are generated in the United States each year. Currently, the greatest volumes of cementitious (high lime) fly ash are used in engineering applications such as concrete products, roadbase materials, and structural fill materials. The remaining unused fly ash is usually pumped to sluice ponds or transported to landfills as waste, constituting long-term waste management problems.
Waste PET plastic is neither environmentally biodegradable nor compostable, which creates disposal problems. Recycling has emerged as the most practical method to deal with this problem, especially with products such as PET beverage bottles. Currently, a large waste stream is available for recycling applications. In the U.S., estimates indicate that production of PET containers will reach 1.8xc3x97106 kg by the year 2000, which is a 55% increase from 1997. Along with increases in waste production, the incentive to develop recycling technologies and value added materials becomes further desirable.
An object of the invention is to provide a composite material from fly ash and recycled, post-consumer waste, chemically unmodified polyethylene terephthalate (PET).
Another object of the invention is to provide a method of making composite material using fly ash and recycled, post-consumer waste, chemically unmodified polyethylene terephthalate (PET).
The present invention provides a composite material and method wherein melted waste, chemically unmodified PET material and fly ash particles are mixed in a container to disperse fly ash particles in the PET material. The resulting mixture then is cooled to solidify the melted PET material to form a composite material having a matrix comprising PET and dispersoids distributed in the matrix and comprising fly ash particles.
In one embodiment of the invention, the solid waste, chemically unmodified PET material and fly ash particles are premixed and placed in the container for melting of the PET material while the mixture is mixed or stirred. Alternately, the solid waste, chemically unmodified PET material can be melted in the container, and fly ash particles introduced to the melted PET material with mixture stirred or mixed. The mixture of fly ash and melted PET material can be molded, extruded or otherwise formed to shaped articles of manufacture or may be used as a protective coating on a substrate.
The invention envisions use of waste PET material from recycled beverage bottles and other sources. In practice of the invention, the recycled waste PET material is not chemically modified in any way prior to melting. The solid recycled waste PET material may be washed in tap water and shredded or otherwise comminuted prior to melting.
The invention envisions use of different types of fly ash particles including relatively high lime, cementitious ASTM class C and/or relatively low lime class F type fly ash. Preferably, the fly ash comprises relatively high lime ASTM class C fly ash and fly ash with comparable morphological characteristics.
Various amounts of fly ash up to about 70 weight % fly ash can be included in the composite material. Preferably, the fly ash content of the composite material is at least 50 weight % and preferably from 50 to 70 weight %.